Pump with mechanical means for effective priming and drip prevention

ABSTRACT

A dispensing device comprising pump for dispensing liquid, the pump comprising a hollow piston moveable within a cylinder, and a valve, controlling the supply of liquid to the piston/cylinder. During a first phase of operation the piston moves outwardly within the cylinder while the valve permits the supply of liquid into the chamber and during a second, subsequent, phase of operation the piston moves inwardly within the cylinder while the valve shuts off the supply of flowable material, with the result that liquid drawn into the chamber during the first phase is pressurized. Arrangements for effective priming and pre-compression of liquid are also described.

DESCRIPTION TECHNICAL FIELD

The present invention relates to pumps, in particular manually actuatedpumps. The present invention further relates to a method of delivering aflowable material using a pump.

BACKGROUND ART

Pumps suitable for spraying or otherwise delivering liquid from acontainer when manually actuated by a user are widely used in the fieldsof cosmetics and household cleaning products. Typically the pump ismounted on the container and communicates with the liquid by means of adip tube. When actuated by a user, the pump draws liquid from thecontainer through the dip tube and into the pump body; and then impelsliquid from the pump body to an outlet.

Various arrangements of pump, outlet and means for user actuation can beused depending on the properties of the liquid to be delivered, desiredoutlet flow conditions and cost. For example, trigger spray pumps suchas described in U.S. Pat. No. 4,161,288, are commonly used to dispensehousehold cleaning products such as liquid detergents or polishes.Finger pumps as described in EP 682 568A, are often used to dispensecosmetic products such as hand lotions or perfumes.

However, known pumps typically comprise 10 to 15 components andtherefore associated tooling, forming and assembly costs are relativelyhigh; yet often with modest operating characteristics.

SUMMARY OF THE INVENTION

It is therefore an aim of preferred embodiments of the present inventionto provide a pump which can be manually actuated, which has goodoperating characteristics in dispensing flowable materials and which isof relatively simple construction. By “flowable materials” we mean inthis specification any non-gaseous material which can be caused to flow,using the present invention, including, without limitation, liquids andviscous materials such as creams and lotions.

Further aims and advantages of preferred embodiments of the presentinvention include ease of manufacture, fast priming, resistance tobottle panelling, and cleanliness after use, as will become apparentwith reference to the description that follows.

According to a first aspect of the present invention there is provided adispensing device comprising a source of a flowable material, a pump fordispensing the flowable material and means for supplying the flowablematerial to the pump, the pump comprising a hollow piston adapted tomove within a cylinder such that the piston and cylinder together definea chamber of variable volume, and a valve controlling the supply offlowable material into the chamber, wherein during a first phase ofoperation of the pump the piston moves outwardly within the cylinder andthe chamber expands, while the valve permits the supply of flowablematerial into the chamber and during a second, subsequent, phase ofoperation of the pump the piston moves inwardly within the cylinder sothat the chamber reduces, while the valve prohibits the supply offlowable material to or from the chamber, with the result that flowablematerial drawn into the chamber during the first phase is pressurised.

The valve preferably has one part which is comprised by or carried withthe cylinder and another part which is comprised by or carried with thepiston.

The valve may comprise an inner cylinder co-operating with a movableinlet valve member which when located within the inner cylinder seals itagainst passage of flowable material therethrough. Suitably the inletvalve member is outside the inner cylinder during one part of thepumping cycle and within the inner cylinder during the remainder of thepumping cycle.

Preferably the pump comprises an outlet valve, preferably an outletpre-compression valve. By this we mean a valve associated with theoutlet, requiring a certain level of force against it, and hence fluidpressure, in order to open and allow the flowable material to escape. Bythis means the output from the dispensing device can be of desirableform (for example a jet or spray). Preferably the pre-compression valveis designed so that when flowable material is being pumped it is openedby the pressurisation of the flowable material, without mechanicalintervention. However during a priming operation when it is air that isbeing compressed, it is preferably arranged not to be opened by the air.Rather, mechanical intervention is required to open the pre-compressionvalve during this phase, and allow the air out. The mechanicalintervention may be the action of a part carried by a body whichcomprises the cylinder, and the pre-compression valve member may be apart of the body which comprises the piston.

According to another aspect of the invention there is provided a pumpcomprising an opening sealable by an outlet valve arranged to be openedby mechanical means acting on a valve member during priming and byhydraulic pressure acting on the valve member as flowable material isdelivered from the pump during a delivery stroke, the valve member beingresiliently biased to seal the opening when the pump is at rest.

According to a further aspect of the invention there is provided a pumpcomprising an opening sealable by an outlet valve arranged to be openedby hydraulic pressure acting on a valve member as flowable material isdelivered from the pump during a delivery stroke, the valve member beingresiliently biased to close the valve when at rest, wherein the pumpfurther comprises mechanical means arranged to open, or hold open, thevalve at the start of a return stroke such that air is drawn through theopening into the pump.

According to yet another aspect of the invention there is provided apump suitable for delivering flowable material from a container, whereinthe pump comprises venting means for selectively opening the containerto the atmosphere during part of a pumping cycle and sealing means whichseals the container from the atmosphere during the remaining part of thepumping cycle, the latter part including when the pump is at rest.

Preferably the pump terminates in an outlet control cap which isrotatable between an operative, flowable material-emitting position andan at-rest, flowable material-blocking position.

The aspects defined above may be used individually or in anycombination; In embodiments in which a non-viscous (ie “thin” or“watery”) liquid is to be pumped any of them may be used and preferredembodiments use all of them. In embodiments in which a viscous materialis to be pumped, for example a lotion or cream, the first and secondembodiments, at least, may be used.

Suitably a pump in accordance with the present invention comprises abody defining the cylinder, with the body preferably comprising, formedas one part with the cylinder, one or more of the following:

-   -   a valve, or part thereof, controlling inflow of flowable        material into the pump;    -   a said mechanical means to assist priming of the pump and/or to        permit suck back of some air through the outlet aperture into        the pump;    -   an actuator for the pump (for example a handle or lever);    -   a shroud for the pump; and    -   an integrally moulded spring.

Suitably a pump in accordance with the present invention Comprises abody defining the piston, with the body preferably comprising, formed asone part with the piston, one or more of the following:

-   -   a valve or part thereof controlling inflow of the material into        the pump;    -   an outlet control cap having “on” and “off” conditions (which        may suitably be moulded as part of the body which comprises a        cylinder, and removed therefrom, and attached to the body        comprising the piston, for example by snap-fitting); and    -   said outlet valve.

Alternatively such parts which may be integrally formed as a part of thebody which comprises the cylinder or piston can be made separatelytherefrom, and joined thereto.

The dispensing device may include a dip tube allowing flowable materialto be drawn into the pump.

As noted above, in certain embodiments the outlet control cap can bemoulded with one of the other parts, for example with the body whichincludes the cylinder, and “snapped” out of it. It may then be attached,preferably in a snap-fit manner, to the body defining the piston. In apreferred such embodiment the control cap is snapped out of theactuator, itself preferably moulded as part of the body.

Preferably a pump defined herein is part of a dispensing device which isdesigned to be hand-held.

In accordance with a further aspects of the present invention there isprovided a method of dispensing a flowable material comprising the useof a dispensing device or pump of any aspect previously defined.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the accompanying diagrammatic drawings. For ease ofexplanation parts are shown separate which may otherwise be moulded as asingle component. In the drawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a pump according to a firstembodiment of the present invention for mounting on the neck of a bottlecontaining a thin liquid to be dispensed;

FIG. 2 is a side sectional view of the pump mechanism of the pump ofFIG. 1, in a rest position but with an outlet control cap thereofconfigured for use;

FIG. 3 is a side sectional view of the pump mechanism of FIG. 2 in anintermediate position of the return stroke;

FIG. 4 is a side sectional view of the pump mechanism of FIG. 2approaching the end of the delivery stroke;

FIG. 5 is a side sectional view of the pump mechanism of FIG. 2 at theend of the delivery stroke;

FIG. 6 is a side sectional view of the pump mechanism of FIG. 2 in arest position with the outlet control cap configured for storage ortransportation; and

FIG. 7 is a cross sectional view of the zone indicated by arrows in FIG.5.

DETAILED DESCRIPTION OF THE IVENTION

FIG. 1 shows a pump 2 according to a first aspect of the presentinvention ready for use, and in the rest position. The pump assembly 2is for mounting on the threaded neck of a bottle (not shown) by means ofa threaded retaining ring 4. The bottle contains a liquid, namely anaqueous, non-viscous, cleaning liquid.

The body 6 of the pump is a single plastics moulding providing:

an inner upright cylinder 8 which snugly receives the upper end of a diptube 10;

an outer upright cylinder 12 having a flared lower end 14 which istrapped against the bottle neck by the retaining ring 4, to secure thepump firmly on the neck of the bottle;

an inner horizontal cylinder 16 communicating via an aperture 18 withthe inner upright cylinder 8 (and hence with the dip tube 10);

an outer horizontal cylinder 20 selectively communicating with the innerhorizontal cylinder 16 and with an outlet 22 (as will be described indetail);

a cover wall or shroud 24 covering the four cylinders just described;and

a trigger lever 26 connected by a flexible moulded-in hinge 28 to theshroud 24.

The second horizontal cylinder surrounds the first horizontal cylinderand, in this embodiment, is longer than it.

Also shown are further features of the body 6 comprising a ventingaperture 30 in the wall of the outer cylinder 20, mechanical means inthe form of an arcuate finger 32 (see FIGS. 2 and 7) projecting from theend of the inner horizontal cylinder 16, and an abutment for a helicalspring 34 (see FIG. 1), the abutment being formed by the frontal portionof the outer upright cylinder 12 and, on the top of the outer cylinder,by a ledge 36.

With reference now to FIG. 2, a second part comprises a shuttle 38having an inlet valve member 40, which in certain positions of theshuttle makes a sealing fit inside the inner horizontal cylinder 16,and, coaxial with it, a piston 42 which at all times makes a sealing fitinside the outer horizontal cylinder 20. The inlet valve member 40 isitself in the shape of a cylinder, and has a widened, flared distal end44.

The piston has on its outer surface two annular sealing skirts. Onesealing skirt 46 forms the termination of the wall of the piston, albeitoutwardly flared. The other sealing skirt 48 is spaced a small distancefrom the sealing skirt 46 and takes the form of a dependent pieceprojecting outwardly from the outer horizontal piston. Each sealingskirt comprises a portion 50 projecting in an outward, oblique directiondirectly from the wall of the piston, and a terminal portion 52 which isparallel to the main wall of the piston.

The shuttle is made of a material with some flexibility, for examplepolyethylene, or a thermoplastic elastomer.

Preferably the shuttle is made of a more flexible material than thebody. The body may typically be made of polypropylene.

It will be seen from the drawings that an outlet control cap 54 ismounted on the shuttle, but that it is of separate manufacture. In factit is moulded as part of the body 6 within the lever 26, and is snappedout of it, and snap-fitted on the shuttle 38.

The valve member 40 and outer piston 42 both face towards the aperture18 of the body 6, being carried on one side of a thick transverse wall56 of the shuttle 38. This wall terminates in an annular outer formation58 which is domed in cross-section, as shown in FIGS. 2 to 6. The outletcontrol cap 54 is snap-fitted onto this annular formation, the cap 54having a correspondingly-shaped annular recess formed therein. Formedlongitudinally through the transverse wall 56 is a port 60. Port 60 isin the form of an arcuate slit which accommodates the arcuate finger 32sufficiently loosely that liquid can flow through the slit even when thearcuate finger is in the slit (see FIG. 7). Liquid drawn from the bottlehas to pass through the port 60. The port 60 leads to an outlet valve 62which leads in turn to the outlet aperture 22 formed in the cap 54 (tobe described in more detail later).

The inner valve member, the outer piston, the transverse wall 56 and thevalve member 62 and its associated parts may all be moulded in oneoperation from a single material. However in another embodiment it maybe desirable to mould the valve member 64 of the valve from a separatematerial and to join it to the rest of the shuttle 38, in order that thevalve member 64 has different flexibility characteristics.

The valve member 64 comprises a plug 66 resiliently biased against avalve opening 68 by its own diaphragm 70; all forming part of theshuttle 38.

The outlet control cap 54 may be turned relative to the shuttle.Downstream of the valve opening 68 there is a bore 61 leading to anaperture 72. As can be discerned in FIGS. 2 to 6 the aperture 72 has araised annular rim 74 around it. Downstream of the aperture 72 there isa route for liquid through a standard swirl chamber, so that the liquidissues through outlet aperture 22 as a fine spray.

The cap 54 has a transverse wall 76 at the end of the pump, breachedonly by the outlet aperture 22. Depending from this wall are an outercylindrical wall 78 and an inner cylindrical wall 80. These cylindricalwalls are coaxial and are of the same length. It is in the innercylindrical wall 80 that there is formed the annular recess to receivethe annular projection 58 of the transverse wall 56 of the shuttle 38.The valve 62 is located within the inner cylindrical wall 80. To beprecise, the valve 62 is located in a de facto chamber bounded by theinner cylindrical wall 80, the transverse wall 56 of the shuttle, andthe transverse wall 76 of the cap. The inner and outer cylindrical wallsof the cap are coaxial with the inner and outer cylinders of the body 6,but the outer cylindrical wall 78 of the cap overlaps the outer wall ofthe body by an amount sufficient to accommodate the helical spring 34(see FIG. 1). The helical spring acts to urge the shuttle and bodyapart, into the rest position shown in FIGS. 2 and 6. For clarity thehelical spring is not shown in FIGS. 2-6.

The inner cylindrical wall of the cap has, on a quadrant of its innercylindrical surface, a raised land 82 (see FIGS. 6, 7). It will be notedthat in the region of numeral 82 the wall is shown thicker in FIG. 6than in FIGS. 2 to 5, and that in FIG. 6 it is in contact with theannular rim 74. When the land 82 is in contact with the annular rim 74around the aperture 72, the cap is in its closed position and liquidcannot be dispensed by the pump. If the cap is turned, by 90° in thisembodiment, the land is moved away from its sealing position and liquidcan flow through the aperture 72 and to the outlet 22. This is thecondition shown in FIGS. 2 to 5 in which it will be seen that there is adiscrete gap between the inside surface of the inner cylindrical wall ofthe cap and the annular rim 74.

In use, depressing the lever 26 by a user causes movement of the cap 54and shuttle 38 relative to the body 6 against the bias of the spring 34,and subsequent movement of the shuttle 38 back to the rest position,under the bias of the spring 34, causes liquid to be drawn up the diptube 10, through the aperture 18 thence via the pump, to the outlet 22.Further detail of the operation of the pump 2 will now be given withreference to FIGS. 2 to 6.

Initially, the pump 2 is configured in the rest position as shown inFIG. 6, with the cap in the “off” position.

In this rest position, the inner valve member 40 is located just beyondthe extent of the inner horizontal cylinder 16. In this position theventing aperture 30 is located between the sealing skirts 46, 48 of theshuttle 38. The valve 62 is also closed. Accordingly, even if the bottleis shaken or inverted there is no route for liquid to escape.

The first task is to turn the cap to the “on” position shown in FIG. 2,by turning it through 90°. In so doing, the lever couples to twotrunnions (not shown) protruding from the outer wall of the cap suchthat in the “on” position movement of the lever is transferred to theshuttle 38.

At the start of the operation the chambers and channels of the pump 2are likely to be filled with air. Before the pump 2 can dispense anyliquid from the supply within the container it must be primed. Priminginvolves flushing out the air in the various chambers and channels ofthe pump 2 so that they are filled with liquid. The pump is primed by auser causing reciprocating movement of the shuttle 38 relative to thebody 6 against the bias of the spring 34, and subsequent movement of theshuttle 38 back to the rest position under the bias of the spring 34. Itis desired that the priming operation involves a minimum number ofstrokes of the shuttle 38 before liquid is dispensed from the pump 2.The pump shown is adapted to minimise the number of strokes required forpriming, preferably not more than 3 on average, more preferably not morethan 2 on average.

As the shuttle 38 is moved from the rest position of FIG. 2, it assumesthe intermediate position shown in FIG. 3. In the intermediate position,the valve member 40 has moved into the inner horizontal cylinder 16, andas a result the outer horizontal cylinder 20 encompasses a closedchamber. The outer piston 42 moves further into the outer horizontalcylinder 20 compressing the air in the closed chamber. The pressure inthe closed chamber increases, but sufficient air pressure is notdeveloped to open the valve 62 by forcing the plug 66 away from thevalve opening 68 against the bias of the diaphragm 70. Rather, it isopened by the arcuate finger 32 coming into contact with the diaphragm70, and mechanically lifting the plug 66 from the valve opening 68against the bias of the diaphragm 70. Opening the outlet valve 62 bymechanical means such as the arcuate finger 32 towards the end of thedelivery stroke of the pump 2 allows pressurised air to be evacuatedfrom the outer horizontal cylinder 20 in spite of the bias of thediaphragm 70 tending to close the outlet valve 62 and the relativelyhigh compressibility of air (compared with liquids).

As the shuttle 38 returns towards the rest position from the end of thedelivery stroke, pressure within the pump chamber defined between theshuttle and the outer horizontal cylinder decreases, to belowatmospheric pressure. This causes a number of significant effects,including the following.

Firstly, as the shuttle 38 first starts to move from the end of thedelivery stroke, the outlet valve 62 is still held open by the arcuatefinger 32. This momentarily causes suction of air back through theoutlet aperture 22. The benefits of this suction will be described laterwith reference to normal (non-priming) operation of the pump 2.Following disengagement of the arcuate finger 32 from the diaphragm 70the outlet valve 62 closes.

Secondly, an under-pressure is formed in the outer horizontal cylinder20.

As the shuttle 38 returns to the rest position the valve member 40 movesbeyond the inner cylinder 16, causing liquid to flow through the innercylinder 16 and into the outer cylinder 20 to relieve the under-pressureconditions developed.

The number of strokes required to prime the pump 2 will depend on therelative dimensions of the cylinders and the dip tube. If the outercylinder 20 is not primed with liquid following one stroke, furtherstrokes are required. The opening of the outlet valve 62 by the arcuatefinger 32 toward the end of the delivery stroke during priming allowsair to be fully evacuated from within the outer cylinder 20 in spite ofthe bias of the diaphragm 70 tending to close the outlet valve 62,thereby maximising the effect of each priming delivery stroke, andconsequently reducing the number of priming strokes required for givencylinder and dip tube dimensions. In the absence of the arcuate finger32, towards the end of each priming delivery stroke the relativecompressibility of air means that insufficient pressure may be generatedin the outer cylinder 20 to open the outlet valve 62, and consequentlyair would be retained in the outer cylinder 20 thus reducing the effectof each priming delivery stroke.

Once the pump 2 has been primed, it is ready to dispense liquid.Dispensing operation is described below.

Again, the shuttle 38 is moved from the rest position, to theintermediate position shown in FIG. 3. In the intermediate position, thevalve member 40 has moved within the inner cylinder 16. The positioningof the valve member 40 within the inner cylinder 16 makes the outercylinder 20 a closed volume. The outer piston 42 moves into the outercylinder 20, compressing the liquid in the closed volume. As the liquidis effectively incompressible, the pressure in the closed volume rapidlyincreases, causing the outlet valve 62 to open under hydraulic pressureon the diaphragm 70 of the outlet valve 62. Liquid passes through theport 61, through the aperture 72, through an insert or swirlconfiguration to break up the liquid into spray and to impart swirl, andis dispensed from the outlet 22.

On the other hand if the user does not apply sufficient force the valve62 will not be opened by the hydraulic pressure. The user must exert athreshold force to develop sufficient hydraulic pressure to open thevalve. This ensures that when the flowable material issues it does so ina desired form (for example, as a fine spray, in this embodiment).

The characteristics of the cap 54 and/or aperture can be varied toproduce a spray or other desired dispensing conditions as appropriate tothe liquid being dispensed.

FIG. 3 also shows that the venting aperture 30 is now open, which meansthat the small underpressure in the bottle is relieved.

The arrangement eliminates or reduces “panelling” of the bottle. Onlytowards the rest position, when the venting is not needed, is theventing means closed, by being covered by the shuttle's sealing skirts46, 48 to each side, and by the portion of the piston 42 which connectsthem (as shown in FIG. 2).

Liquid is dispensed from the outlet aperture 22 until the end of thedelivery stroke. FIG. 5 shows the pump 2 at the end of the deliverystroke. At this position movement is terminated by the abutment of theend of the outer cylinder of the body against the underside of thetransverse wall 76 of the cap.

As the shuttle 38 returns toward the rest position from the end of thedelivery stroke, the pressure within the shuttle 38 is lost. This causesa number of effects.

First, as the shuttle 38 first starts to move from the end of thedelivery stroke, the outlet valve 62 is now maintained open by thearcuate finger 32. This causes suction of some air back through theoutlet aperture 22 and the channels which feed it. This drives liquidwhich is left in the outlet aperture 22 and the adjacent channelsinwardly, reducing drips and preventing blockage from any non-volatileresidue which could otherwise dry out in the channels.

Following disengagement of the arcuate finger 32 from the diaphragm 70the outlet valve 62 closes.

Second, liquid is drawn into the first cylinder 16 through the inletaperture 18.

Third, an under-pressure is formed in the chamber defined by the shuttle38 and outer cylinder 20.

As the shuttle 38 returns to the rest position the inlet valve member 40moves beyond the inner cylinder 16, allowing the liquid in the innercylinder 16 to be drawn into the outer cylinder 20 by the pressuredifference between them. Thus the outer cylinder 20 remains primed withliquid, and the pump 2 is ready to dispense liquid from the outletaperture 22 upon further actuation by a user.

The pumps referred to can be incorporated into a trigger mechanism. Thisformat is especially suitable for dispensing household cleaningproducts, including “thin” liquids such as liquid detergents, polishes,and horticultural products such as insecticides, fungicides and foliarfeeds; and also thicker liquids, for example liquid soaps, shampoos,hair conditioners, creams, lotions, sauces, syrups; being, for example,cleaning products, cosmetics products, healthcare products (for exampleskincare treatments) and food products.

Alternatively, the pumps can be incorporated into a finger pumpmechanism. This format is especially suitable for dispensing “thick”cosmetic and beauty liquid products such as hand lotions andmoisturizing creams. Alternatively the pumps can be incorporated into afinger spray mechanism. This format is especially suitable fordispensing “thin” cosmetic and beauty products such as perfumes. In thelatter embodiments the liquid would not issue from the end face of thecap, as shown in FIGS. 1 to 6, but from an outlet aperture in adifferent location; for example from the side of the cap or through aspout extending from the cap. The end face would be left free to bepressed upon.

Although the pumps referred to have been described as comprisingcylinders, it is clear to the skilled person that this does not limitthe scope of the invention to embodiments comprising cylinders ofcircular cross section. Any suitable cross section such as square,rectangular or elliptical can be used providing the associatedpiston/valve member has a complementary cross-section, and therespective parts co-operate. Likewise, references to horizontal andvertical are merely made for clarity and understanding, and not to betaken as limiting.

Although the invention has been described in detail with reference to alever-actuated pump (commonly known as a trigger pump) the inventivedevelopments described herein could be used in a pump with a differentactuation mechanism, for example a push-down mechanism, as used for afinger spray or a lotion dispenser, the latter suitably having adownwardly-facing outlet displaced from the container proper by a stem.Flowable materials typically dispensed by a finger spray includeperfumes and air fresheners, provided in the container as a liquid anddispensed as a fine spray. Flowable materials typically dispensed by apress-down dispenser include relatively viscous liquids, for exampleliquid soaps, shampoos, hair conditioners, creams, lotions, sauces,syrups; being, for example, cleaning products, cosmetics products,healthcare products (for example skincare treatments) and food products.

1. A dispensing device comprising a source of a flowable material, apump for dispensing the flowable material and means for supplying theflowable material to the pump, the pump comprising a hollow pistonadapted to move within a cylinder such that the piston and cylindertogether define a chamber of variable volume, and an inlet valvecontrolling the supply of flowable material into the chamber, whereinduring a first phase of operation of the pump the piston moves outwardlywithin the cylinder and the chamber expands, while the inlet valvepermits the supply of flowable material into the chamber; and during asecond, subsequent, phase of operation of the pump the piston movesinwardly within the cylinder so that the chamber reduces, while theinlet valve prohibits the supply of flowable material to or from thechamber, with the result that flowable material drawn into the chamberduring the first phase is pressurized, the pump further comprising anopening sealable by an outlet valve which is arranged to be opened byhydraulic pressure acting on the outlet valve as flowable material isdelivered from the pump during a delivery stroke, wherein a bodydefining the piston of the pump comprises an outlet control cap havingon and off conditions and also comprises said outlet valve associatedwith said outlet control cap, and by the fact that the pump comprisesmechanical means which are part of a body defining the cylinder of thepump and which are constantly accommodated at least partly inside a portof the body defining the piston, such that the mechanical means, first,are arranged to open, in a priming phase, the outlet valve during theend of a delivery stroke and to hold open the outlet valve at the startof a return stroke as well as, second, allow that the outlet control capis rotatable relative to the body defining the piston.
 2. A dispensingdevice according to claim 1 wherein the inlet valve has one part whichis comprised by or carried with the cylinder and another part which iscomprised by or carried with the piston.
 3. A dispensing deviceaccording to claim 1 wherein the inlet valve comprises an inner cylinderco-operating with a movable inlet valve member which when located withinthe inner cylinder seals it against passage of flowable materialtherethrough.
 4. A dispensing device according to claim 1 wherein thebody defining the cylinder comprises one or more of the following: (a)the inlet valve, or part thereof, controlling inflow of flowablematerial into the pump; (b) an actuator for the pump; (c) a shroud forthe pump; and (d) an integrally moulded spring.
 5. A dispensing deviceas claimed in claim 1 having a pre-compression outlet valve or adispensing outlet valve.
 6. A dispensing device according to claim 1,wherein the pump comprises venting means for selectively opening acontainer to the atmosphere during part of a pumping cycle and sealingmeans which seals the container from the atmosphere during the remainingpart of the pumping cycle, the latter part including when the pump is atrest.
 7. A dispensing device according to claim 1, wherein the bodydefining the piston comprises the inlet valve, or part thereof,controlling inflow of the flowable material into the pump.